How to End a Program in Java
Java, being a versatile and robust programming language, offers various ways to terminate a program. Whether you are developing a simple application or a complex system, understanding how to properly end a program is crucial for ensuring smooth execution and resource management. In this article, we will explore different methods to end a program in Java, including the use of the System.exit() method, returning from the main method, and terminating threads.
Using System.exit()
One of the most common ways to end a Java program is by using the System.exit() method. This method is defined in the java.lang.System class and allows you to terminate the program immediately. When System.exit() is called, it closes all open resources, terminates all threads, and exits the Java Virtual Machine (JVM). Here’s an example:
“`java
public class Main {
public static void main(String[] args) {
System.out.println(“Program started.”);
// Perform some operations
System.out.println(“Program is ending.”);
System.exit(0); // Exit with status code 0
}
}
“`
In the above example, the program starts by printing “Program started.” and then performs some operations. After that, it prints “Program is ending.” and calls System.exit(0) to terminate the program. The status code 0 indicates that the program has ended successfully.
Returning from the main method
Another way to end a Java program is by returning from the main method. This method is useful when you want to terminate the program based on a specific condition or after performing certain operations. Here’s an example:
“`java
public class Main {
public static void main(String[] args) {
System.out.println(“Program started.”);
// Perform some operations
if (someCondition) {
return; // Terminate the program
}
System.out.println(“Program is ending.”);
}
}
“`
In this example, the program starts by printing “Program started.” and then performs some operations. If the condition `someCondition` is true, the program terminates immediately. Otherwise, it continues to execute and prints “Program is ending.” before terminating.
Terminating threads
In addition to ending the main program, you may also need to terminate threads that are running concurrently. Java provides the `Thread.interrupt()` method to interrupt a thread, which can be used to terminate it. Here’s an example:
“`java
public class Main {
public static void main(String[] args) {
Thread thread = new Thread(() -> {
try {
// Perform some operations
Thread.sleep(10000); // Sleep for 10 seconds
} catch (InterruptedException e) {
System.out.println(“Thread was interrupted.”);
}
});
thread.start();
// Wait for the thread to finish
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(“Main program is ending.”);
}
}
“`
In this example, a new thread is created and started. The thread sleeps for 10 seconds before being interrupted. The `InterruptedException` is caught, and a message is printed. Finally, the main program waits for the thread to finish and then prints “Main program is ending.” before terminating.
Conclusion
Ending a program in Java can be achieved through various methods, including using System.exit(), returning from the main method, and terminating threads. Understanding these techniques will help you manage your programs effectively and ensure proper resource management. By choosing the appropriate method based on your requirements, you can create robust and reliable Java applications.
